A measurement has been performed on the time that muon neutrinos take to travel from their production point at CERN to the Opera detector, finding that neutrinos take a handful of nanoseconds less than if they were traveling at light speed, experimental particle physicist (CERN and Fermilab) and blogger Tommaso Dorigo reports.

Neutrinos seen by the Opera detector are produced when a high-intensity spill of protons from the SpS hits a target in the CERN laboratories, he says. The large flow of pions and kaons results downstream of the collisions; these particles are then focused and allowed to decay to muons and muon neutrinos, and the latter travel underground to the Gran Sasso, where, once in a while, one of them is detected.

“Measuring with great accuracy the timing of the whole process is not so hard, since the protons hit the target at very precise times and the Opera detectors can indeed record these interactions with nanosecond accuracy.

“What is impossible to know with precision, IMHO, is the fine structure of the proton spill.  The protons arrive at the target with a time-bunched structure, but the details of the spill structure are not known in great detail — the ‘bunches’ might be very sharp peaks of intensity or have straggling tails, for instance.”